Method and Apparatus for Channel Estimation of Transmission Channels with Memory in Digital Telecommunications Systems, and Corresponding Computer-Program Product

1. A method for executing, as a function of a received signal, a procedure of channel estimation of a transmission channel with memory in a telecommunications system, the method comprising: estimating a delay spread associated to said channel, said estimating the delay spread including calculating a root mean square value of delay spread by evaluating crossings with a threshold level of a characteristic curve of a transfer function representing said channel, said evaluating of crossings including evaluating a first number of crossings, corresponding to a real part of said transfer function, and a second number of crossings, corresponding to an imaginary part of said transfer function, with the threshold level corresponding to a zero level; applying a mean operation to said first number of crossings and said second number of crossings, to obtain a mean number of crossings, wherein said telecommunications system operates according to an OFDM modulation; obtaining a value of rough estimation of the channel by demodulating the received signal; and supplying said root mean square value of delay spread to an operation involving fine channel estimation.

2. The method according to claim 1 wherein said root mean square value of delay spread is obtained, via a relation of direct proportionality, from said mean number of crossings.

3. The method according to claim 1 , further comprising: calculating said root mean square value of delay spread according to said value of rough estimation of the channel.

4. The method according to claim 1 wherein said telecommunications system is a system of a wireless type, including an IEEE 802.11a WLAN standard or an HyperlanII WLAN standard.

5. An apparatus for performing, as a function of a received signal, a channel estimation in a transmission channel with memory in a telecommunications system, the apparatus comprising: a module configured to estimate a delay spread associated to said channel, by calculating a root mean square value of delay spread by evaluating crossings with a threshold level of a quantity associated to a transfer function representing said channel, said module is configured to perform said evaluation of crossings by evaluating a first number of crossings, corresponding to a real part of said transfer function, and a second number of crossings, corresponding to an imaginary part of said transfer function, with the threshold level corresponding to a zero level, and said module further being configured to apply a mean operation on said first number of crossings and said second number of crossings to obtain a mean number of crossings; a first module configured to calculate a value of rough estimation of the channel by demodulating the received signal; and a second module of fine channel estimation that receives said root mean square value of delay spread.

6. The apparatus according to claim 5 wherein said module configured to estimate the delay spread associated to said channel is configured to calculate said root mean square value of delay spread via a relation of direct proportionality from said mean number of crossings.

7. The apparatus according to claim 5 , wherein the first module is further configured to supply said value of rough estimation to said module configured to estimate a delay spread as a function of said value of rough estimation.

8. The apparatus according to claim 5 wherein the module comprises part of a receiver for OFDM telecommunications systems.

9. The apparatus according to claim 5 wherein said module comprises part of a receiver of a wireless telecommunications system, including a receiver compatible with an IEEE 802.11a WLAN standard or a HyperlanII WLAN standard.

10. A computer-readable medium including contents that, when loaded into a memory of a computer, cause the computer to implement a method comprising: estimating a delay spread associated to a channel according to a root mean square value of delay spread based on crossings of a characteristic curve of a transfer function representing a channel, at least some of the crossings being associated with a threshold level; evaluating a first number of crossings, corresponding to a real part of the transfer function, and a second number of crossings, corresponding to an imaginary part of said transfer function, with the associated threshold level of the crossings corresponding to a zero level; and applying a mean operation, to the first number of crossings and to the second number of crossings, to obtain a mean number of crossings; obtaining a value of rough estimation of the channel by demodulating a received signal; and supplying the root mean square value of delay spread to an operation involving fine channel estimation.

11. The computer-readable medium of claim 10 wherein the method includes determining the root mean square value of delay spread from the mean number of crossings using a direct proportionality relation.

12. The computer-readable medium of claim 10 wherein the method includes: determining said root mean square value of delay spread according to the value of rough estimation of the channel.

13. A system to perform channel estimation of a communication channel, the system comprising: a module adapted to estimate a delay spread associated with the channel according to a root mean square value of delay spread, the root mean square value of delay spread being based on crossings with a threshold level of a quantity associated with a transfer function representing the channel, wherein the module is adapted to evaluate the crossings by evaluating a first number of crossings, corresponding to a real part of the transfer function, and a second number of crossings, corresponding to an imaginary part of the transfer function, with the threshold level of the crossings corresponding to a zero level, and wherein the module is further adapted to apply a mean operation on the number of crossings and on the second number of crossings to obtain a mean number of crossings that can be used to estimate the delay spread associated with the channel; and a first unit to obtain a value of rough estimation of the channel by demodulating a received signal; a second unit communicatively coupled to the first unit to determine the root mean square value of delay spread; and a third unit coupled to the second unit to perform fine channel estimation based on the root mean square value of delay spread.

14. The system of claim 13 wherein the module is adapted to estimate the delay spread associated with the channel, using the mean number of crossings, based on a direct proportionality relation.

15. The system of claim 13 , wherein the second unit is communicatively coupled to the first unit to determine the root mean square value of delay spread according to the value of rough estimation of the channel obtained by the first unit.

16. A method for executing, as a function of a received signal, a procedure of channel estimation of a transmission channel with memory in a telecommunications system, the method comprising: estimating a delay spread associated to said channel, said estimating the delay spread including calculating a root mean square value of delay spread by evaluating crossings with a threshold level of a characteristic curve of a transfer function representing said channel, said evaluating of crossings including evaluating a first number of crossings, corresponding to a real part of said transfer function, and a second number of crossings, corresponding to an imaginary part of said transfer function, with the threshold level corresponding to a zero level; and applying a mean operation to said first number of crossings and said second number of crossings, to obtain a mean number of crossings, wherein said telecommunications system operates according to an OFDM modulation, wherein said root mean square value of delay spread is obtained by calculating a root mean square value of said mean number of crossings but for a corrective factor that takes into account a contribution of noise on the calculation of the crossings with said zero level, said corrective factor being proportional to an inverse of a signal-to-noise ratio.

17. An apparatus for performing, as a function of a received signal, a channel estimation in a transmission channel with memory in a telecommunications system, the apparatus comprising: a module configured to estimate a delay spread associated to said channel, by calculating a root mean square value of delay spread by evaluating crossings with a threshold level of a quantity associated to a transfer function representing said channel, said module is configured to perform said evaluation of crossings by evaluating a first number of crossings, corresponding to a real part of said transfer function, and a second number of crossings, corresponding to an imaginary part of said transfer function, with the threshold level corresponding to a zero level, and said module further being configured to apply a mean operation on said first number of crossings and said second number of crossings to obtain a mean number of crossings, and said module further being configured to calculate said root mean square value of delay spread by calculating a root mean square value of said mean number of crossings but for a corrective factor that takes into account a contribution of noise on the calculation of the crossings with said zero level, said corrective factor being proportional to an inverse of a signal-to-noise ratio of the channel.

18. A computer-readable medium including contents that, when loaded into a memory of a computer, cause the computer to implement a method comprising: estimating a delay spread associated to said channel according to a root mean square value of delay spread based on crossings of a characteristic curve of a transfer function representing a channel, at least some of the crossings being associated with a threshold level; evaluating a first number of crossings, corresponding to a real part of the transfer function, and a second number of crossings, corresponding to an imaginary part of said transfer function, with the associated threshold level of the crossings corresponding to a zero level; applying a mean operation, to the first number of crossings and to the second number of crossings, to obtain a mean number of crossings; and determining the root mean square value of delay spread by calculating a root mean square value of the mean number of crossings, along with a corrective factor to account for noise contribution.

19. A system to perform channel estimation of a communication channel, the system comprising: a module adapted to estimate a delay spread associated with the channel according to a root mean square value of delay spread, the root mean square value of delay spread being based on crossings with a threshold level of a quantity associated with a transfer function representing the channel, wherein the module is adapted to evaluate the crossings by evaluating a first number of crossings, corresponding to a real part of the transfer function, and a second number of crossings, corresponding to an imaginary part of the transfer function, with the threshold level of the crossings corresponding to a zero level, wherein the module is further adapted to apply a mean operation on the number of crossings and on the second number of crossings to obtain a mean number of crossings that can be used to estimate the delay spread associated with the channel, and wherein the module is further adapted to determine the root mean square value of delay spread by calculating a root mean square value of the mean number of crossings, along with a corrective factor to account for noise contribution.